Petunias have been under cultivation at least since 1870 when seeds of wild species in Argentina were collected by the French botanist Petun. Petunia hybrida is thought to have arisen from intercrossing between at least two species, Petunia axillaris and Petunia violacea, or possible Petunia inflata, while under cultivation. The resulting variation in color and flower form has exceeded that found in the parental species.
Breeding and selection for novel traits was conducted almost immediately after introduction to cultivation. The various forms now available including the single and double, multiflora and grandiflora types, were developed in the late 1800's. Pure breeding lines were first developed in the 1920's. Breeding efforts intensified during the 1950's when the first F.sub.1 multiflora hybrid became commercially accepted. Virtually all commercial petunia varieties currently in use are F.sub.1 hybrids.
Petunia species are primarily self pollinating. Petunia breeding in the past 30 years has focused on the performance of the plant in the pack for the bedding plant trade. A "pack" consists of a small disposable plastic, multi-celled container used for growing plants for retail sale. Packs used for petunias commonly have an individual cell soil volume of 7-8 cubic inches. Breeding emphasis has been on characteristics such as earliness, compactness, and color range, as well as performance in the garden. The popularity of petunias over the years is due in part to their ability to withstand a wide variety of conditions as well as the range of colors and types available. They have consistently been one of the top species used for bedding plant production and held the number one position for many years. They are currently second after impatiens (Impatiens wallerana).
Detailed information about petunia breeding, diseases, agronomic traits can be found in Bedding Plants, John W. Mastalerz (Ed.), Pennsylvania Flower Growers, 1976 and in Petunia, Kenneth C. Sink (Ed.), Springer-Verlag, 1984.
Single flowered grandiflora (GF) petunias are by far the most popular type. Grandifloras are distinguished from multifloras (MF) by having a larger flower and stockier plant habit. The second most popular type is the single multiflora, which has more branches and a greater ability to come back into flower after adverse weather conditions. Grandiflora and multiflora doubles share a relatively small portion of the market.
To date, there has not been a simple method of reducing the plant and flower size to a size smaller than the current commercial cultivars. It would be desirable to have new types and forms of petunia for the commercial market, especially desirable would be a reproducible method of reducing plant and flower size in commercial petunia varieties.